Multi-function centrifugal blower unit

ABSTRACT

A two-stage centrifugal fan section with a first suction inlet, a central diffuser chamber section accepting the first section discharge and having circumferentially spaced second and third suction inlets, and a final generally tangentially discharging centrifugal fan section receiving diffuser section discharge, all incorporated in a composite housing to form a motor-blower unit with an induction motor section of which the fan mounting rotor shaft is supported in a housing end wall offset from the housing axis to provide with a local pinch formation in the final section interior, a scroll or snail shell type discharge. The diffuser section is vaned to isolate and allocate certain flows to respective regions of the final fan inlet and thereby promote stable pumping operation at the three inlets independently at distinct flow and/or pressure differential conditions.

United States Patent Gilliland MULTI-FUNCTION CENTRIFUGAL BLOWER UNIT[75] Inventor: Michael L. Gilliland, Kent, Ohio [73] Assignee: Ametek,Inc., New York, NY.

[22] Filed: May 18, 1972 [21] Appl. No.: 254,760

[52] US. Cl. 415/219 C, 415/198 [51] Int. Cl. F0ld 1/02, FOld 25/24,Fold 9/00 [58] Field ofSearch 415/198, 199 A,2l9 R,2l9 C,

[111 3,790,300 [451 Feb. 5, 1974 Primary Examiner- -Carlton R. CroyleAssistant Examiner-Louis J. Casaregola Attorney, Agent, or Firr n-PhilipD. Golrick ABSTRACT A two-stage centrifugal fan section with a firstSuction inlet, a central diffuser chamber Section accepting the firstsection discharge and having circumferentially spaced Second and thirdsuction inlets, and a final generally tangentially dischargingcentrifugal fan Section receiving diffuser Section discharge, allincorporated in a composite housing to form a motor-blower unit with aninduction motor section of which the fan mounting rotor Shaft issupported in a housing end wall offset from the housing axis to providewith a local pinch formation in the final section interior, a scrollorsnail shell type discharge. The diffuser Section is vaned to isolate andallocate certain flows to respective regions of the final fan inlet andthereby promote stable pumping operation at the three inletsindependently at distinct flow and/or pressure differential conditions.

10 Claims, 7 Drawing Figures PAIENTED 51974 33790300 sum 2 or 5 FIGZ 'PATENTEBFEB 51974 FiGB SHEU 3 BF 5 PATENTEU 51974 3 790 300 SHEET 6 BF 5PAIENTEDFEB 1 14 3.700.300

sum 5 0r 5 FIG? MULTI-FUNCTION CENTRIFUGAL BLOWER UNIT Though in itsbroader aspect the present invention has application to other fluids andto handling simultaneously of distinct fluids, especially in the samestate, it will be hereinafter discussed and a particular embodimentdescribed in terms of the pumping of air, as a fluid handled in threestreams for different services and performances.

Where it is required to pump or move simultaneously two or more distinctstreams of air at different rates and/or distinct pressure conditions,especially where stable operations are required for each stream,hitherto there have been used either a single pump and motor of adequatecapacity and a system of pressure and flow controls, or separaterespective pumps or blowers powered by respective motors, though attimes with the pumps driven from a common motor shaft. Thismultiplication of components has been necessary in prior practice toisolate the air streams or flows from each other in order to providestable operations at the desired conditions for each service in questiongenerally as an alternative to using comparatively expensive pressureand flow controlling devices to the same end.

Such multiplicity of components often entails decided disadvantages ininstallations where space is at a premimum, or mounting areas limited,or weight is desirably to be kept low; and obviously entails furtherexpense both for material and other manufacturing costs in the severalcomponents, as well as for their mounting in the environment of use.

The present invention enables the pumping or two or more air streams atdifferent air flow rates and/or pressure differentials by a singleelectric motor powered suction or blower unit having a respective inletfor each stream and discharging to atmosphere through a common outlet,and obtaining stable respective performance for the air moving funtioncorresponding to each inlet. Further a particular embodiment isdisclosed representing compact and economic blower unit structure whichis obtainable by application of the broader aspects of the invention.

In the particular embodiment of the invention hereinafter described, airis centrifugally pumped for three different services connected to therespective housing inlets, at respectively different flow rates and twodifferent pressure differentials, by a first fan section providing theperformance required for two services and by a second fan sectiondischarging ultimately to the first providing the performance requiredfor a third service; for all of which the fans are driven commonly onone motor shaft; the total air of all three services discharged througha common outlet to atmosphere. Between the fan sections, there isprovided a diffusing chamber section guiding and delivering air from thedischarge of the second mentioned fan section and from the first andsecond named inlets, to the eye or intake of the first named centrifugalfan section in a manner which attains the stable operation and pumpingunder the desired conditions for the three services.

In the so-called diffuser section, the three air streams enter near theperiphery, the discharged air of the second-mentioned fan section mixingwith the air of one of the diffuser section direct inlets, and the mixedair stream and the stream from the other direct inlet are separatelydirected to a central inlet or eye, for the final fan sectiondischarging to atmosphere by respective series of inward fixed diffuservanes. Two of the vanes, as divider vanes, begin at the diffusercircumferential wall and run inward to the eye to divide the chamberinto two flow spaces, respectively corresponding to the service inletsopening to the chamber, the remaining intervening blades or vanes ineach series terminating short of the circumferential wall to permit flowfrom the circumferential wall inwardly.

By the location of the inner ends of the divider vanes on thecircumference of the eye to the final impeller chamber, flow space atthe eye is allocated percentagewise corresponding to the percentage ofthe total mass flow in the blower represented by the air intended toenter the corresponding division of the diffuser section chamber.

In the particular circumstances, as in an embodiment here disclosed,where the pressure differentials under which the air streams move arenot greatly different from each other, and the air is subjected toactual pressure not much different from the atmospheric, suchproportioning of the flow may be based upon the volume flow rates.

The combination with the diffuser enables the two fan sections to handlethe three air streams with distinct stable performances, thoughtransiting a common fan, so that practically the plurality of servicesmay be handled in one compact unit.

The immediate consequent advantages in savings of component costs, insimplified and space-saving installation, and opportunity for overallsystem weight reduction, for example, while attaining desiredperformances, are obvious. Further in the disclosed embodiment of theinvention, particular impeller disposition and impeller housing form andstructure is disclosed based on a generally cylindrical form, yetproviding a good approximation to a scroll housing and discharge, whichsimplifies fabrication and tooling design with attendant cost savingsfor-the type of structure and function achieved It is the general objectof the present invention to provide a fluid pump unit with centrifugalimpellers on a common driven shaft capable of moving a plurality offluid streams with stable performance.

A further object of the invention is to provide a centrifugal air bloweror suction unit with impeller driven by a common motor shaft capable ofmoving air for a plurality of services drawn in at respective housinginlets and discharged from a common outlet of a final impeller sectionhandling the total air flow.

A further and more specific object in the particular disclosedembodiment is to provide a scroll type discharge impeller housingsection in a relatively simple and low cost manner.

Other objects and advantages will appear from the following descriptionand drawings wherein:

FIG. 1 is an elevational view, for convenience of reference denominateda front end elevation, of an electric motor-blower unit embodying theinvention;

FIG. 2 is a side view, partly in elevation and partly in irregularsection taken generally as indicated by 22 in FIG. 1;

FIG. 3 is primarily a front elevational view of a blower housing membershowing certain details of an intermediate or diffuser chamber structurein the unit;

FIG. 4 is a rear view of the housing component constituting theprincipal part of FIG. 3;

FIGS. 5 and 6 are fragmentary detail elevations of FIG. 3 viewed asindicated at 55 and 6-6; and

FIG. 7 is a front view of a second housing member.

GENERAL ARRANGEMENT The drawings show an electric motor driven blower orsuction unit embodying the invention comprising (see FIGS. 1 and 2) amotor M united with blower B, which pumps air for three differentservice requirements, therefore handles three different air streams,drawn into the respective inlets, P,Q,R, and discharges the total of theair through one unit outlet D. Merely to establish a convenient basisfor description, the orientation of FIG. 2 is used for top, bottom,front and back relations, the left end being considered the front of theunit.

In a composite blower housing later described, centrifugal impeller F-lon the motor shaft S in a chamber adjacent motor M peripherallydischarges to outlet D; at the opposite end of the housing, the shaftcarries two like centrifugal impellers F2 and F-3 housed in a twostagearrangement drawing in air at inlet R; and in what, relative to thefinal fan F-l and its chamber, may be termed an antechamber receivingdirectly the air streams entering inlets P, Q, and also the air streamentering R and discharged from the two-stage impellers, a diffuser-likestructure Z controls air flow to F-l.

The important diffuser structure Z, efficiently directs, as to twostreams mixes, and introduces the air streams through a common innerwall eye aperture I providing an inelt to and aligned with adjacentcentral intake or eye of impeller F-l, so that the total air handledmoves without any appreciable interaction upon the air movingperformance the blower for the three air streams which it brings intothe respective inlets.

HOUSING AND IMPELLERS Circumferentialy surrounding shell portions andcertain transverse walls for the above described structures are providedby members 11, 12, l3, 14 in a composite housing basically cylindricalin design shape apart from certain divergencies for the outlet D andinlet P, wherein the axis X-s of the motor shaft S is paralleloffsetupwardly and to the right from the cylinder axis X-c, as viewed from thefront end and designated in a FIG. 3 for example.

The right side of cylindrical portion 12a is fitted endwise onto aninterrupted circular flange llr on the left face of wall 11b in arabbet-type joint; a shallowly cupped front end cap member 13 has itsinternally rabbetted shallow cylindrical rim 13a fitted onto theexternal rabbet left end of the cylindrical rim wall or shell portion12a; and the open right rim or shell end 11a is fitted on a generallyrounded disk-like end member 14, at an inward flange 14a spaced from themargin forming in effect a rabbet. These blower housing elements 11, 12,13, 14 are primarily secured by external longitudinal bolts 15 throughprojecting apertured lugs 13b and 14b of the end members; but screws 16locally hold respective upwardly projecting parts of members 11, 12forming the inlet P.

Member 14 in elevational outline diverges from circular in matchingmember 1] to form the outlet D and discharge structure for the chamberof impeller F-l, Coaxially about an integral bearing socket formation Mewith axis offset from the circular center as required for the shaft, ashort rabbeted cylindrical flange 14f accepts motor field cylindricalhousing 17 fitted thereon and in turn having a rabbeted motor endbracket member 19 similarly fitted on its opposite end. With externalbolts 18 through radially projecting lugs 19a and threaded into bosses14g on member 14, the latter serves both as an outer end wall for thechamber of impeller F-l, hence of the blower housing, and also as ashaft bearing supporting motor end bracket. It may be noted here thatmotor M is appropriately an induction motor.

The support is generally conventional for the impellers, with therespective end disks centrally clamped by spacer washers and sleeves 21,22, 23, 24 between the inner race of bearing 25 and clamping nut 26threaded on the shaft S; and so also sheet metal structure of eachimpellerinsofar as comprising an end disk centrally apertured for theshaft S, an annular disk having a large central opening as the impellereye or intake, and a series of appropriately formed vanes or blades withedge nibs or lugs projecting through corresponding apertures of andheaded down against the disks in rivet like fashion to secure theimpeller components into a rigid assembly. Stationary sheet metal diskor wall elements 28 and 31 are similarly secured on stationary vaneslater described.

As integral parts of housing member 12, a transverse round partition orwall 12b, on its left side as seen in FIG. 2, has a series of integralvanes 12v angularly spaced about a large central circular opening l2doffset from the cylindrical axis corresponding to the shaft offset; thevane free edges mounting a sheet metal end disk 28, parallel to 121; andcentrally apertured for a running clearance with spacer 23, thusdefining a first stage impeller chamber and forming a so-calledstationary fan, conducting air discharged peripherally from the firststage impeller F-3, around the edge of 28 equally peripherally spacedfrom 12a, back inwardly toward the shaft to discharge through 12d intothe aligned intake eye of second stage impeller F-2. These structuresare conventional except for a certain asymmetry imposed by the axisoffset, the vanes 12v originating in wall 12a and running with likeinclinations to and equally angularly spaced about 12d. (See FIG. 7).

The oblique tubular inlet formation 13c for the inlet R opens throughthe end wall 13d of member 13 over an area spanning and generallysymmetrically disposed relative to the eye of the first stage impeller.

The peripheral wall portion continues to the rear (right in FIG. 2) ofwall 12b in cylindrical form to closely fit a circular disk 31, carriedon the edges of the internal vanes of member 1 1, defining the chamberfor the second stage impeller F-2.

Integral external mounting pad formations 12f align with like shorterpad formations 11f to form unit mounting feet. Otherwise the exterior ofthe member 12 is cylindrical, except for the forwardly oblique hollowupward projection 12p, the open back (right in FIG. 2) side of which isclosed by a matching flat projection 11p of member 11, secured locallyby screws 16 to form inlet P. The shape of the inlet structure P isgathered from FIGS. 1, 2, 3 and 4.

For the inlet O, an opening in the cylindrical wall portion 12a at thelocation shown (at left in FIG. 1) is provided with an inserted sleevefor attachment of an air conduit, as also may be done at P and R tosimplify fabrication ofmembers l1, 12, 13 as say die castings.

The represented directions of the centerline of the inlets-P, Q, R, andthe outlet D are dictated by the particular intended environment of usefor the specific motor blower unit here shown, except as may beotherwise here specified.

The lower margin of member 12 at the lower region as cast is recessed orrelieved to accommodate a projecting part (dotted at US in FIG. 2) ofoutlet structure provided on member 11. Particulars of the chamber andoutlet structure for the final impeller F-3 are described below.

In the housing component ll, at the left end of the circumferentialshell portion 11a, the integral partition 11b having the previouslymentioned circular opening or eye I offset from the cylindrical axis tobe concentric with the shaft, thus provides the inner or left end wallof the chamber defined with 11a and 14 for impeller F-l, having an inletaligned with the impeller intake eye. In the bottom part of the housing(see FIGS. 1, 2, 3, 4,) the peripheral wall 1 1a diverges tangentiallyfrom cylindrical, widening out in radial sense into the more orlesstangential-shell wall portion l lt running into the outlet structureD, while above the latter, an integral formation 11h (see FIG. 4) curvesinward away from the cylindrical portion of rim 11a forming a pinchregion approaching theedge of the impeller F-3 and then rounding into astraight portion 11k continued out into a top wall of outlet D; 11h and11k being notched adjacent 11a to accommodate the flange 140.

As well in the lower region beginning well before 1 It, the wall 11b hasan arcuately extending or annular sectorially shaped forward offset 11s,as seen in FIG. 2 offset to the left in the right end region of member11, which also gives a larger flow area leading toward the outlet D (seeFIG. 3).

As previously mentioned, the lower region of member 14 diverges from around or disk shaped to a matching form to close the back of member 11including the right side (as viewed in FIG. 2) of outlet D.

The above described shell peripheral formations conjoined with theaforementioned offset of the rotor shaft axis (upward and to the rightas viewed in FIG. 1) gives a good approximation by simple structure to asnail shell peripheral casing shape in which the flow space for theperipheral discharge of impeller F-l is radially expanding, in acircumferential direction, (counterclockwise, the direction of impellerrotation as viewed in FIG. I) from the pinch 11h around to the outlet D,with, moreover, an axial enlargement of the flow space near the outletD, as provided by the offset 11s.

DIFFUSER STRUCTURE-ANTECIIAMBER The structure of the antechamber anddiffuser section is best seen and discussed relative to FIG. 3 inconjunction with FIG. 2.

- On the generally flat front or left face of the common inner wall llb,as well as flange llr, there is a series of projecting integral fixedblades or vanes with inner ends terminating at the opening I, thecoplanar left edges of which support the sheet metal disk 31 formingalso the front wall of the diffuser or antechamber. The shape anddisposition of the vanes or blades relative to the eye opening I intothe last impeller chamber and relative to the inlets P and Q, and alsorelative to the dividing the annular flow space to and about the eye Iinto respective sectors corresponding to inlets P and O; that is,counter clockwise between 11x to 11y, providing flow space from inlet Qto the eye I, and from 11y to 1 1x flow space from inlet P to the eye I.The further diffuser vanes or blades llz, have outer ends spaced fromthe housing shell portion 12a, for distribution of each of the airflows; all of these vanes, excepting 11x, and of this the inner end,running radially to the edge of the eye or discharge aperture I.Outwardly beyond a portion running radially from the edge of the walleye aperture which is the vane portion effectively dividing the arcuateextent of the aperture for flow purposes, the vane llx is angled backclockwise (as viewed from the front, see FIG. 3) to accommodate adesired location of inlet O, which in the fitted shell portion 12a islocated just counter clockwise of the outer end of 11x.

Further, over the lower sector handling air from Q, running counterclockwise from a radius just below the location of the inlet Q toward11y, the margin of wall disk 31 is incised with spaced notches, betweenwhich the residual edge tabs (here thirteen) are twisted about 45 toslope inwards in the counterclockwise direction, thereby forming aseries of louvers or peripherally located diffuser blades 31b in whatrepresents the discharge from the second stage impeller chamber and theinlet to the antechamber for the air stream ultimately entering thecasing at R.

The annular sectorial offset 11s of the wall 11b into the antechamberspace, which happens to fall under the series of blades or vanes 31b,does not impair the efficient entry of the air from Q and the twostageimpeller, and as may be noted in FIGS. 3 and 5, the left or clockwiseend of the offset sector 11s curves or blends upwardly from the mainplane face of 11b to the maximum offset which yet is well spaced fromwall 31, and at the right end (see FIG. 6) tapers or slopes somewhatinto the outlet D. The flange formation llr, though interrupted for theregion of inlet P, is carried up with the offset 11s to provide therabbeted type joint even in the recessed region of 11a accommodates theoffset.

The inner ends of the dividing blades or vanes llx and 11y are solocated that the peripheral space about, and for flow to, theeyel intothe final impeller section is allocated according to the mass flow whichis intended to be handled in each sector of the chamber. In other words,the arcuate extent of the eye to which each sector feeds is directlyproportional to that fraction or percentage of the total mass flow intothe eye which is represented by the mass flow in the sector.

Thus the arcuate extent of the eye to which P feeds, thecounterclockwise arc from llx to lly at the eye, is proportional to theratio of the flow into inlet P to the total flow; the balance of the eyeperiphery, to ratio of the sum of the mass flows into Q and R to thetotal flow.

In a particular blower unit, it was desired to produce a flow of 40 cfmof air at a vacuum of 8 inches of water at R, a flow of 25 cfm at 3inches at Q, and a flow of 115 cfm at a vacuum of 3 inches at P,representing a flow total of 180 cfm discharged from D; the air flowbeing stated in terms of air at standard conditions. Since the pressuresinvolved and the difference in the pressure conditions between therequired performance were small, the volume flow rates were acceptablyused in place of mass flow rates in the ratios determining the diffuserstructure. Accordingly in a blower unit as shown and describeddischarging to free atmosphere the periphery of the eye I to which Pdischarged was selected tobe about 250 (1l5/l80 X 360); the remaining130 (65/l80 X 360) allocated to the combined flows from Q and R.Efficient stable performance for all the three functions was attained;and even where an increased flow to 50 cfm was allowed at R, the otherperformances were substantially maintained, apparently by virtue of thedivision of the antechamber, though the eye periphery allocation thenbut roughtly approximated the flow percentage relations.

By way of further'example, were only the stated flow and pressuredifferentials involved at P and R, then with the two stage impellerdischarge at the periphery of a set of blades llz without need of thelouvers 31b, the dividing vanes 11x and 11y would be located to allocaterespectively to each 50/ 165 X 360 and ll/l65 360 of the periphery of l.

I claim:

l. A multi-function fluid pump comprising:

a centrifugal impeller with a central intake opening;

a housing portion surrounding said impeller providing an impellerchamber having a fluid outlet, and an inner wall apertured to provide aneye opening to and aligned with the intake of said impeller;

a second housing portion forming an antechamber discharging through theeye aperture into the impeller intake, and having first and secondinlets for respective pump-moved fluid streams opening to theantechamber at regions spaced angularly from each other about the axisof and radially outwardly from, said aperture;

and means dividing the circumferential space in said antechamber into atleast two annular sectors each receiving a fluid stream from arespective inlet and directing each sector discharge into said eyeaperture at a respective peripheral portion of said aperture, said meansincluding a diffuser-like, fluidguiding vaned structure for saidsectors.

2. A pump as described in claim 1, wherein:

said means dividing the antechamber into said sectors directs thedischarge of each sector to an eye aperture peripheral portion at leastroughly proportional to the respective percentage of the mass flow offluid in the sector relative to the total mass flow intended to entersaid impeller.

3. A pump as described in claim 1, including,

a second centrifugal impeller on a common shaft with the first impellerand a further housing portion therefor, disposed adjacent theantechamber oppositely from the first said chamber and having an inletfor a third moved fluid stream and an outlet to one of the two firstnamed inlets of the antechamber.

4. A pump as described in claim 3, wherein:

said antechamber has three inlets, including at least one as a pumpinlet through a circumferential wall of the antechamber into arespective said sector; and in an antechamber end wall, a series oflouvered openings, into the last said sector, said series serving asanother of the said three inlets and receiving the third streamdischargefrom the outlet of the housing for the second said impeller.

5. As a multi-function blower for gaseous fluids, the fluid pump asdescribed in claim 1, wherein:

said first and second inlets open through a circumferential wall of, anddischarge respective inlet gas streams into, the said antechamber;

said antechamber including a second wall spaced parallel from theapertured said inner wall with said inlets opening into the spacebetween said walls; the said second wall having a series of vaneddiffusing louvers opening into one of said annular sectors; said pumpincluding a second centrifugal impeller on a common shaft with the firstimpeller, and surroundedby a further housing portion,

said further housing portion providing a third inlet in communicationwith the intake of the respective impeller, and a discharge path for athird respective gas stream from the second impeller through said louverseries to the antechamber.

6; A blower as described in claim 5, wherein:

said louvers slope inwardly to said'antechamber in the direction ofrotation of the first said impeller; and

the annular sector with which said louver series is associated extendsin the direction of first impeller rotation away from the respectiveinlet.

7. A blower as described in claim 5 for moving air in three distinctstreams into respective inlets of the blower and commonly dischargingthe air, wherein:

said means dividing the antechamber into said sectors directs thedischarge of each sector to an eye aperture peripheral portionapproximately proportional to the respective percentage of the airvolume flow in the sector relative to the total air volume flow intendedto enter said eye aperture.

8. An air blower as described in claim 5, wherein:

a first housing member as an integrally cast structure provides the saidinner wall of generally circular shape, a generally cylindricalcircumferential wall extending from one side of the inner wall on oneend, to peripherally surround the said first impeller, and open at itsother end, a radial extension of said inner wall, a circular shortflange on the other side of said inner wall but coaxial with thecircumferential wall and interrupted over the locus of said extension,and vanes within the circle of, but projecting from the said inner wallaxially beyond, the said flange to provide said means dividing theantechamber and the said diffuser-like structure around said eyeaperture; second housing member as an integral structure provides agenerally cylindrical wall portion with both ends open and one endfitted on said interrupted flange, a hollow radially outward projectiondiverging from the cylindrical wall portion at the said one end closedby the radial extension of said inner wall to form an inlet to one saidsector; sheet metal disk, equal in diameter to and coaxially alignedwith said flange, is secured on the said vanes and, as an end wall, withthe cylindrical portion of the second housing member and the inner wallof the first member defines said antechamber, said disk having, over aportion of its circumference overlying the other said sector, a seriesof spaced notches defining tabs each twisted thereby forming saidlouvers; w

an end cap member providing an end wall has a rim fitted to the otherend of said cylindrical portion of the second housing member, anddefines therewith and with said sheet metal disk a centrifugal impel-'ler housing for impeller means including the second said impeller, saidcap member having a central inlet to the said impeller means;

a disk-like housing end closure member is fitted on the open end of thefirst housing member to define therewith a chamber for the first saidimpeller, said end closure member including a bearing socket formationreceiving a bearing for an impellersupporting shaft;

said members secured together as a composite blower housing by externallongitudinal bolts through integral lugs on the respective peripheriesof said end cap and closure members.

9. A blower as described in Claim 8, wherein:

said end closure member has said socket on the outer side thereof with ashort circular flange concentric thereabout; and a motor is provided bya stator field housing fitted to the last said flange a rotor providingthe said shaft with one end extending through said bearing andsupporting said impellers, and a motor end bracket member supporting abearing for the other shaft end;

said stator field housing and the bracket member being secured to saidblower housing by longitudinal bolts through the end bracket member andthreaded into the said end closure member thereby to form amotor-powered blower unit.

10. A pump as described in claim 8, wherein:

the circumferential wall portion of the first housing member isgenerally cylindrical over its major extent, and has an integralexternal outlet formation incomplete at the open end of the firsthousing member and there covered by a matching extension of the closuremember, the circumferential wall portion on one side of the outletformation curving inwardly from cylindrical as a pinch formation withinthe respective impeller chamber and on the other side of the outletcarried out tangentially into one side of the outlet formation;

and the shaft axis is parallel offset from the housing cylindrical axisin a direction away from the tangential portion and toward the pinchformation;

said inner wall of the first housing member being axially offset towardsaid antechamber along a sector within the interrupted flange adjacentsaid tangential wall portion to afford a discharge region axialenlargement;

whereby an approximation to a snail shell casing and discharge isprovided for the first said impeller.

1. A multi-function fluid pump cOmprising: a centrifugal impeller with acentral intake opening; a housing portion surrounding said impellerproviding an impeller chamber having a fluid outlet, and an inner wallapertured to provide an eye opening to and aligned with the intake ofsaid impeller; a second housing portion forming an antechamberdischarging through the eye aperture into the impeller intake, andhaving first and second inlets for respective pump-moved fluid streamsopening to the antechamber at regions spaced angularly from each otherabout the axis of and radially outwardly from, said aperture; and meansdividing the circumferential space in said antechamber into at least twoannular sectors each receiving a fluid stream from a respective inletand directing each sector discharge into said eye aperture at arespective peripheral portion of said aperture, said means including adiffuser-like, fluidguiding vaned structure for said sectors.
 2. A pumpas described in claim 1, wherein: said means dividing the antechamberinto said sectors directs the discharge of each sector to an eyeaperture peripheral portion at least roughly proportional to therespective percentage of the mass flow of fluid in the sector relativeto the total mass flow intended to enter said impeller.
 3. A pump asdescribed in claim 1, including, a second centrifugal impeller on acommon shaft with the first impeller and a further housing portiontherefor, disposed adjacent the antechamber oppositely from the firstsaid chamber and having an inlet for a third moved fluid stream and anoutlet to one of the two first named inlets of the antechamber.
 4. Apump as described in claim 3, wherein: said antechamber has threeinlets, including at least one as a pump inlet through a circumferentialwall of the antechamber into a respective said sector; and in anantechamber end wall, a series of louvered openings, into the last saidsector, said series serving as another of the said three inlets andreceiving the third stream discharge from the outlet of the housing forthe second said impeller.
 5. As a multi-function blower for gaseousfluids, the fluid pump as described in claim 1, wherein: said first andsecond inlets open through a circumferential wall of, and dischargerespective inlet gas streams into, the said antechamber; saidantechamber including a second wall spaced parallel from the aperturedsaid inner wall with said inlets opening into the space between saidwalls; the said second wall having a series of vaned diffusing louversopening into one of said annular sectors; said pump including a secondcentrifugal impeller on a common shaft with the first impeller, andsurrounded by a further housing portion, said further housing portionproviding a third inlet in communication with the intake of therespective impeller, and a discharge path for a third respective gasstream from the second impeller through said louver series to theantechamber.
 6. A blower as described in claim 5, wherein: said louversslope inwardly to said antechamber in the direction of rotation of thefirst said impeller; and the annular sector with which said louverseries is associated extends in the direction of first impeller rotationaway from the respective inlet.
 7. A blower as described in claim 5 formoving air in three distinct streams into respective inlets of theblower and commonly discharging the air, wherein: said means dividingthe antechamber into said sectors directs the discharge of each sectorto an eye aperture peripheral portion approximately proportional to therespective percentage of the air volume flow in the sector relative tothe total air volume flow intended to enter said eye aperture.
 8. An airblower as described in claim 5, wherein: a first housing member as anintegrally cast structure provides the said inner wall of generallycircular shape, a generally cylindrical circumferential wall extendingfrom one side of the inner wall on one end, to peripherally surround thesaid first impeller, and open at its other end, a radial extension ofsaid inner wall, a circular short flange on the other side of said innerwall but coaxial with the circumferential wall and interrupted over thelocus of said extension, and vanes within the circle of, but projectingfrom the said inner wall axially beyond, the said flange to provide saidmeans dividing the antechamber and the said diffuser-like structurearound said eye aperture; a second housing member as an integralstructure provides a generally cylindrical wall portion with both endsopen and one end fitted on said interrupted flange, a hollow radiallyoutward projection diverging from the cylindrical wall portion at thesaid one end closed by the radial extension of said inner wall to forman inlet to one said sector; a sheet metal disk, equal in diameter toand coaxially aligned with said flange, is secured on the said vanesand, as an end wall, with the cylindrical portion of the second housingmember and the inner wall of the first member defines said antechamber,said disk having, over a portion of its circumference overlying theother said sector, a series of spaced notches defining tabs each twistedthereby forming said louvers; an end cap member providing an end wallhas a rim fitted to the other end of said cylindrical portion of thesecond housing member, and defines therewith and with said sheet metaldisk a centrifugal impeller housing for impeller means including thesecond said impeller, said cap member having a central inlet to the saidimpeller means; a disk-like housing end closure member is fitted on theopen end of the first housing member to define therewith a chamber forthe first said impeller, said end closure member including a bearingsocket formation receiving a bearing for an impeller-supporting shaft;said members secured together as a composite blower housing by externallongitudinal bolts through integral lugs on the respective peripheriesof said end cap and closure members.
 9. A blower as described in Claim8, wherein: said end closure member has said socket on the outer sidethereof with a short circular flange concentric thereabout; and a motoris provided by a stator field housing fitted to the last said flange , arotor providing the said shaft with one end extending through saidbearing and supporting said impellers, and a motor end bracket membersupporting a bearing for the other shaft end; said stator field housingand the bracket member being secured to said blower housing bylongitudinal bolts through the end bracket member and threaded into thesaid end closure member thereby to form a motor-powered blower unit. 10.A pump as described in claim 8, wherein: the circumferential wallportion of the first housing member is generally cylindrical over itsmajor extent, and has an integral external outlet formation incompleteat the open end of the first housing member and there covered by amatching extension of the closure member, the circumferential wallportion on one side of the outlet formation curving inwardly fromcylindrical as a pinch formation within the respective impeller chamberand on the other side of the outlet carried out tangentially into oneside of the outlet formation; and the shaft axis is parallel offset fromthe housing cylindrical axis in a direction away from the tangentialportion and toward the pinch formation; said inner wall of the firsthousing member being axially offset toward said antechamber along asector within the interrupted flange adjacent said tangential wallportion to afford a discharge region axial enlargement; whereby anapproximation to a snail shell casing and discharge is provided for thefirst said impeller.